The invention is directed to a method for measuring a means for manufacturing electrical assemblies, particularly for coordinate-related equipping of printed circuit boards with components, whereby a test plate having the nature of a printed circuit board is equipped with wafer-like simulations of the components at defined placement points by the means.
It was previously standard to employ a glass panel similar to a printed circuit board as test plate, this comprising centering marks in its corner regions. The glass panel provided with a two-sided adhesive foil is inserted into the means fashioned, for example, as automatic equipping unit, whereupon the position of the centering marks is identified with a topically resolving printed circuit board camera of the automatic equipping unit. The test plate is then equipped with simulations of components at locations defined relative to the center marks.
In a following method step, the equipped glass panel is inserted into an optical measuring machine. The glass laminae comprised defined markings whose position relative to the centering marks of the glass plate are identified in the measuring machine. Correction values are determined from the positional deviations from the desired ideal position in the coordinate directions and in view of the rotated attitude, these correction values being input as correction parameters into the automatic equipping unit that takes these deviations into consideration during later equipping of printed circuit boards with components.
The invention is based on the object of simplifying and speeding up the determination of the correction parameters.
This object is achieved by the invention according to claims 1 and 6.
A pre-condition is thereby that the local reference marks are applied on the test plate with high precision. Such a precision can be achieved, for example, with the assistance of photolithographic processes. It is possible to forego a marking in the simulations and to instead employ, for example, the outside edges of the simulations as defined structure features. In such cases, it is advantageous to employ appropriate ceramic or metal parts instead of the glass laminae, the edges thereof being easily recognizable.
The critical advantage of the method is comprised therein that it is now no longer the global position of the simulations that is measured relative to the global reference marks of the test plate; rather, only narrow excerpts are observed and measured. A high-precision measuring machine is not required for such measuring procedures. The slight distances between the structure features and the local markings make it possible, given slight measuring errors to identify the positional deviations of the simulations with, for example, the assistance of simple optical measuring devices.
Advantageous developments of the invention are identified in the following claims:
As a result of the features of claim 2, the relative position of the reference marks relative to the structure features of the simulations can be identified at one go without having to move the sensor. Measuring imprecisions are thus only dependent on the quality of the sensor optics. All other machine influences are thus completely suppressed. The sensor fashioned, for example, as CCD camera is connected to an evaluation electronics wherein the relative position of the structure features to the reference marks is calculated.
Due to the development according to claim 3, the test platexe2x80x94in one clampingxe2x80x94can be equipped with the simulations and can also be measured without additional manipulation, for example with the assistance of the printed circuit board camera. The errors that occur in the centering of the measuring plate are thus eliminated. The equipping of the test plate and the displacement of the printed circuit board camera can be implemented with the assistance of one and the same control device.
After the positional identification has been implemented for all simulations put in place, the systematic deviations are calculated in an evaluation means. This evaluation means can, for example, be a program module incorporated into the control device of the means that communicates the calculated correction parameters, for example, according to claim 4, to the machine control as fixed values without further action.
A particular advantage of such a method is comprised therein that such calibration events can be implemented not only at newly fabricated machines but also at machines already in use, being implemented from time to time without particular outlay and without further auxiliary means, for example, given routine maintenance measures. Modification of the positioning procedures that are caused by wear or aging can thus be checked an corrected with little outlay.
Due to the high speed when measuring the markings, it is possible to employ a high plurality of simulations according to claim 5, so that an adequate plurality of measurements can be implemented for statistical interpretation.
The development according to claim 7 makes it possible to determine the angular position of the simulations in that, for example according to claim 8, the corner regions lying diagonally opposite one another and at a great distance from one another are measured.
As a result of the development according to claim 9, the structure features are length the same optical properties and the reference marks. As a result thereof, the scanning optics can be optimally set since the same distinguishing criteria apply when evaluating the markings as apply when evaluating the reference marks, this facilitating the interpretation.
The simulations according to claim 10 exhibit a good shape stability even at different temperatures. Due to the arrangement of the markings, these and the reference marks lie at the same level, as a result whereof parallax errors are avoided.
The development according to claim 11 makes it possible to also employ non-transparent ceramic material for the simulations instead of transparent material, whereby the markings are then arranged on the upper side.